Electron beam irradiation effects on mechanical relaxation of aromatic polysulphones

Abstract

The effects of electron beam irradiation on the molecular motion of poly(oxy-1,4-phenylenesulphonyl-1,4-phenylene oxy-1,4-phenyleneisopropylidene-1,4-phenylene) (U-PS) and poly(oxy-1,4-phenylenesulphonyl-1,4-phenylene) (PES) were studied by measuring the dynamic viscoelastic properties. The γ relaxation peaks existing at low temperature (−100°C for U-PS, −110°C for PES) shifted to higher temperature and became narrower with increasing dose. A new relaxation (β′ relaxation) appeared upon irradiation in the range from 40°C to just below the glass transition temperature. The magnitude of the β′ relaxation was reduced by heat treatment and this relaxation disappeared in the second run. The β′ relaxation was assigned as a molecular motion during rearrangement induced by chain scission from a loosened chain packing to a more rigid chain packing. The β relaxation peak responsible for the glass transition shifted to a lower temperature with increasing dose. It was concluded from these facts that polysulphones are mainly degraded by chain scission on the sulphone moiety.